Diamonds with grey as the primary dominant colour are unique. These diamonds are comparatively reasonably priced and have a perceived colour resembling the colour of the metal nickel, aluminum, or pewter.
Grey is a neutral colour containing little or no saturation. The addition of small quantities of blue or green will produce a cool grey colour, while the addition of brown or yellow will produce a warm grey colour. Common names for grey colour diamonds include charcoal grey, steel, pigeon, slate, silver etc.
The grey diamond rough is mined in Australia, South Africa, India, Russia and Brazil. Grey diamonds are coloured by hydrogen, and more rarely boron (unknown how, since boron nearly always forms blue). The defect causes the stone to absorb all wavelengths of light equally. grey colour can tint nearly every other shade. grey colours often appear very different when viewed under average natural daylight versus an artificial light source. Natural grey diamonds occur within a specific region of colour tone. Their lightness extends from very light (smoke) grey, through dark (graphite) grey colours. The secondary hues and colour modifiers include black, green, blue, yellow, pink, purple, brown etc. Enhanced grey colours are rarely made due to easy availability of natural grey diamond